Radiation furnace

ABSTRACT

A high-temperature radiation furnace includes an aluminum cylindrical chamber, detachably clamped to an aluminum baseplate, there being gas conduits in the baseplate to supply positive or negative fluid pressure into the chamber and insulated electric conductors upstanding from the base plate to energize a resistance heating coil which encircles a workpiece. The housing cover is of easily rupturable material in case of overpressure and the heating coil is encircled by oppositely disposed, adjustable, radiation shields to restrict and reflect the heat. A variable speed motor-driven hoist is used for raising and lowering the chamber on the baseplate. A sealed vacuum port is provided in the baseplate for connection to a vacuum station.

United States Patent [72] Inventor Thomas C. Athanis 28 Shaw St., West Roxbury, Mass. 02132 [21] Appl. No. 73,866 [22] Filed Sept. 21,1970 [45] Patented Nov. 9, 1971 [73] Assignee Astreon Corporation Lowell, Mass.

[54] RADIATION FURNACE 1 1 Claims, 2 Drawing Figs.

52 u.s.c| 13/31, 263/50 [51] Int. Cl H051) 3/00, F27d 1/00, F27b 5/06 [50] Field ofSearch 13/31, 20; 263/50; 250/108 [56] References Cited UNITED STATES PATENTS 3,257,492 6/1966 Westeren 13/31 3,285,593 11/1966 Tavernellietal. 3,414,661 12/1968 Reed Primary Examiner- Bernard A. Gilheany Assistant ExaminerR. N. Envall, .l r. ArtorneyPearson & Pearson ABSTRACT: A high-temperature radiation furnace includes an aluminum cylindrical chamber, detachably clamped to an aluminum baseplate, there being gas conduits in the baseplate to supply positive or negative fluid pressure into the chamber and insulated electric conductors upstanding from the base plate to energize a resistance heating coil which encircles a workpiece. The housing cover is of easily rupturable material in case of overpressure and the heating coil is encircled by oppositely disposed, adjustable, radiation shields to restrict and reflect the heat. A variable speed motor-driven hoist is used for raising and lowering the chamber on the baseplate. A sealed vacuum port is provided in the baseplate for connection to a vacuum station.

RADIATION FURNACE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrical heating devices, more particularly radiant heating furnaces of the type that utilize gaseous fuels.

2. Description of the Prior Art There are many industrial operations which require very high temperatures, i.e., temperatures in the range of l,000-3 ,000 C. Some of the operations which commonly utilize such temperatures are brazing operations, hydrogen-fired cleaning operations, out-gassing of metal articles, high-temperature coating operations, the melting of high-temperature metals and alloys and the like.

Therefore, there is a rather large demand for high-temperature furnaces, most commonly radiation-type furnaces, which allow the utilization of high temperatures for treating workpieces within a certain limited area. Some of these furnaces are electric-arc-type furnaces, other furnaces are gas-fired fur.- naces wherein the heat of combustion developed by the combustion of the gases is utilized to develop the high working temperatures required by the operator. A characteristic of such furnaces is that they are highly insulated and somewhat cumbersome to handle. Because of their relatively high cost,

high-temperature furnaces should have relatively short heatcool cycles and the zone which is heated should be no larger than that required for the predetermined selective heating of a given workpiece. It should be borne in mind that in most of these cases wherein high-temperature processing is required, any significant unnecessary prolongation of the workpiece to such high temperatures will result in deterioration of the property thereof.

Some furnaces have reasonably good cycle control with pieces of a particular size but do not provide means to achieve an optimum heat-cool cycle with pieces having a range of sizes.

SUMMARY OF THE INVENTION Therefore, it is an object of the instant invention to provide an improved radiation furnace having a relatively short heatcool cycle.

Another object of the invention is to provide a radiation furnace of relatively light weight, yet a furnace which is capable of handling workpieces of surprisingly large size with respect to the mass of the furnace.

Another object of the invention is to provide a radiation furnace having a heating zone which is adjustable in size, thereby facilitating maximum heating efficiency with workpieces of various sizes.

Another object of the invention is to provide a novel means for changing the size of the heating zone in a radiation furnace and for providing novel cooling means whereby those members of the apparatus which lie outside the heating zone are maintained at desirably low temperatures.

Another object of the invention is to provide apparatus having an inexpensive and foolproof overpressure safety relief feature. A

Other objects of the invention will be obvious to those skilled in the art upon reading the instant application.

The above objects have been achieved by providing apparatus containing a novel and adjustably sized heating zone formed by a plurality of arcuate heat-reflecting shields. These shields are so selected with respect to size that optimum quantity of heat initially having radiated from the heating zone is reflected back from the shields onto the workpiece. So effective is this radiating action that the temperature of the wall of the apparatus remains below 80 C. although the temperature of the workpiece may be at 2,000 C.

The radiation shields are preferably formed of tungsten, molybdenum, or tantalum. Preferably at least two sets of the shields are arranged in concentric relation one to the other to achieve the most effective conservation of heat energy. It has been found most advantageous to mount the lateral heat shields in notches mounted on laterally positioned brackets. Such an arrangement allows the relatively easy positioning of the shields prior to heating. However, when heated, the thermal expansion of the shields provides means for maintaining them tightly in the brackets.

In order to make full use of the capacity of the apparatus to reflect heat onto heat zones of varying sizes, the heating coils are made easily replaceable with coils of different sizes. To this end, the electrodes to which the coil is attached are made both horizontally and vertically adjustable.

In one highly advantageous embodiment of the invention, a light metallic foil is used as the cover of the heating chamber, thereby providing an effective and economical safety feature. The foil is readily replaced if it is broken by the undesirable rising of pressure within the heating chamber.

ILLUSTRATIVE EXAMPLE OF THE INVENTION In this application and accompanying drawings there is shown and described a preferred embodiment of the invention and there are suggested various alternatives and modifications thereof, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. These suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be able to modify it and embody it in a variety of forms, each as may be best suited in the condition of a particular case.

FIG. 1 is a partly exploded, partly fragmentary perspective view of the apparatus of the invention.

FIG. 2 shows some detail of the means by which the foil cover is mounted on the apparatus.

Referring to the drawing, it is seen that radiation furnace 10 comprises a cylindrical furnace chamber II having a wall of aluminum 12 which is about 0.25 inch thick and is fastened to baseplate 14 by means of clamp I6 and sealed to the baseplate by means of a circumferential O-ring seal 18. The top of the furnace chamber consists of a furnace cover 20 of easily rupturable sheet material preferably aluminum foil of about a 0.00l-inch thickness. Cover 20 is connected to the furnace chamber by means of bolts 22, by use of a cover ring 24, O- ring seal 23 and upper flange 26 of furnace chamber 11. The cover assembly comprises a handle 27 bolted to the furnace chamber flange and connected by wire rope 21 to a motorized hoist 25 used to assist the lifting of the furnace chamber to allow access to the working parts enclosed therein. Guide rod 28 is provided so that the furnace chamber can be raised and lowered in such a way that it is not rotationally displaced during the time that it is disconnected from the base plate.

The furnace chamber comprises safety shields 30 and 32 each mounted over a viewing window 34 or 36. Each safety shield and viewing window is mounted in front of a safety shutter 38 which is placed in conduit 40 welded into furnace chamber 11. A radiation filter 44 is also mounted in the furnace chamber 11.

Upstanding from baseplate 14 are two electric conductor support rods 45 and 46. Each electrode support rod holds one electrode support 48 or 49. The electrode supports 48 or 49 are adjustably positioned on the support rods by an adjustable split clamping means 50. Moreover, the electrode supports themselves include elongated slots 52 in which a heating coil 54 of molybdenum or tungsten is adjustably positioned by sliding bolts 56. Heating means 55 includes the heating coil 54 which is a resistance heating element. Each of electric conductor support rods 45 and 46 is encircled by an insulating bushing 58 therearound at its point of entry into base 14. Support rod 45 carries an upper vertically adjustable support arm 60 on which is mounted an upper radiation shield 62. Radiation shield 62 is utilized to reflect downwardly any heat that might otherwise be radiated upwardly to impinge on rupturable furnace cover 20. In the center of base plate I4 is mounted a vacuum port cover plate 66 for vacuum port 67. Mounted in and extending upwardly from the vacuum port cover plate 66 is a center support rod or pedestal 68. Center support rod carries (reading upwardly from'the bottom) a gas diffuser plate 64, a lower radiation shield holder 70, and upper radiation shield holder 72, and a work support plate 74. The work support plate 74 is mounted just below heating coil 54 so that a workpiece mounted on work support plate 74 will be positioned in the heating zone generally defined by the heating coil 54. Mounted on diffuser plate 64 are an inner radiation shield 76 and an outer radiation shield 78, each of tantalum, molybdenum or tungsten sheet. Each said lateral radiation shield comprises a concave surface, the vertical edges 80 of which mate with notches 82 of the radiation shield holders 70 and 72. There are four sets of notches on each arm of the radiation shield holders so that it is possible to utilize a plurality of differently sized radiation shield holders depending on the size of the workpiece 90 and the degree to which it is desired to minimize the radiant heat losses from heating coil 54. Two pairs of concentric, inner and outer shields 76 and 78 are illustrated.

In operation of the heater, gas enters the apparatus through base plate 14, gas inlet fitting 84, and gas supply conduit 86. This gas is distributed through gas diffuser plate 64, carried upwardly and escapes through gas exhaust conduit 88 out of the chamber. Usually the chamber 11 is first purged with nitrogen, to fiush out all air, nitrogen being relatively inexpensive. Because nitrogen might form objectionable nitrides if the radiant heating took place in a nitrogen atmosphere, hydrogen is then introduced into chamber 11 to purge the nitrogen.

What is claimed is:

1. ln a furnace having a heating zone and a heating means for subjecting a workpiece to heat in a controlled environment, the improvement which comprises the provision of a plurality of concave, radiation-shielding plates mounted about said workpiece, said plates being spaced apart to define said heating zone therebetween, radiation shield holder means having a plurality of pairs of notches, the lateral edges of each said plate being held in said plurality of pairs of notches on the radiation shield holder means mounted in said furnace.

2. A furnace of the type defined in claim 1 wherein at least two pairs of said plates are mounted about said workpiece, in a substantially concentric relation one pair to the other pair.

3. A furnace of the type defined in claim 1 comprising additionally a heat shield plate mounted above said workpiece and above said lateral shields and forming means to refiect heat downwardly onto said workpiece.

4. A furnace of the type defined in claim 1 wherein said heating means is a resistance coil detachably connected at each end with electrodes, and wherein said electrodes are horizontally and vertically adjustable thereby to accommodate coils of different sizes.

5. A furnace as defined in claim 1 comprising means to conduct gas along each workpiece.

6. A furnace as defined in claim 1 and comprising an easily rupturable metal foil top on said furnace.

7. A furnace as defined in claim 1 having an aluminum wall.

8. A high-temperature radiation furnace comprising a cylindrical casing detachably mounted on a circular base plate and having a circular top wall of rupturable sheet material adapted to fracture at a predetermined pressure above atmosphere,

a workpiece support pedestal within said casing, said pedestal including a workpiece platform, and

a plurality of notched, horizontal holders, each detachably supporting one of a pair of opposed, concave, bendable, heat radiation shields for reflecting heat back to said workpiece and restricting the heat zone therearound, electric resistance heating means within said casing, said means including a heating coil adapted to encircle a workpiece mounted on said platform and including horizontally and vertically adjustable electrode split clamfglmeans supporting said coil between said plates; gas d1 slon means incorporated Into said circular base plate, for flowing gas into said casing and upwardly around said workpiece, and

upstanding electric conductor rods insulatively mounted in said base plate and supporting said split clamp means within said casing.

9. A furnace of the type defined in claim 8 comprising additionally a heat shield plate mounted above said workpiece and above said lateral shields and forming means to reflect heat downwardly onto said workpiece.

10. A furnace as defined in claim 8 and comprising an easily rupturable metal foil top on said furnace.

11. A furnace as defined in claim 8 having an aluminum wall.

t i i i 4 

1. In a furnace having a heating zone and a heating means for subjecting a workpiece to heat in a controlled environment, the improvement which comprises the provision of a plurality of concave, radiation-shielding plates mounted about said workpiece, said plates being spaced apart to define said heating zone therebetween, radiation shield holder means having a plurality of pairs of notches, the lateral edges of each said plate being held in said plurality of pairs of notches on the radiation shield holder means mounted in said furnace.
 2. A furnace of the type defined in claim 1 wherein at least two pairs of said plates are mounted about said workpiece, in a substantially concentric relation one pair to the other pair.
 3. A furnace of the type defined in claim 1 comprising additionally a heat shield plate mounted above said workpiece and above said lateral shields and forming means to reflect heat downwardly ontO said workpiece.
 4. A furnace of the type defined in claim 1 wherein said heating means is a resistance coil detachably connected at each end with electrodes, and wherein said electrodes are horizontally and vertically adjustable thereby to accommodate coils of different sizes.
 5. A furnace as defined in claim 1 comprising means to conduct gas along each workpiece.
 6. A furnace as defined in claim 1 and comprising an easily rupturable metal foil top on said furnace.
 7. A furnace as defined in claim 1 having an aluminum wall.
 8. A high-temperature radiation furnace comprising a cylindrical casing detachably mounted on a circular base plate and having a circular top wall of rupturable sheet material adapted to fracture at a predetermined pressure above atmosphere, a workpiece support pedestal within said casing, said pedestal including a workpiece platform, and a plurality of notched, horizontal holders, each detachably supporting one of a pair of opposed, concave, bendable, heat radiation shields for reflecting heat back to said workpiece and restricting the heat zone therearound, electric resistance heating means within said casing, said means including a heating coil adapted to encircle a workpiece mounted on said platform and including horizontally and vertically adjustable electrode split clamp means supporting said coil between said plates; gas diffusion means incorporated into said circular base plate, for flowing gas into said casing and upwardly around said workpiece, and upstanding electric conductor rods insulatively mounted in said base plate and supporting said split clamp means within said casing.
 9. A furnace of the type defined in claim 8 comprising additionally a heat shield plate mounted above said workpiece and above said lateral shields and forming means to reflect heat downwardly onto said workpiece.
 10. A furnace as defined in claim 8 and comprising an easily rupturable metal foil top on said furnace.
 11. A furnace as defined in claim 8 having an aluminum wall. 